This invention relates to digital communications systems and in particular to systems embodying asynchronous transfer mode (ATM) technology.
The asynchronous transfer mode (ATM) technology is a flexible form of transmission which allows any type of service traffic, voice, video or data, to be multiplexed together on to a common means of transmission. In order for this to be realised, the service traffic must first be adapted typically into 53 byte cells comprising 5 byte headers and 48 byte payloads such that the original traffic can be reconstituted at the far end of an ATM network. This form of adaptation is performed in the ATM adaptation layer (AAL).
A discussion of ATM adaptation of narrow band traffic is given in specification No GB-A-2,290,433 (EP 9411944) which describes a system and method in which an adaptive virtual junctor is used to adapt an ATM switch to perform a narrow band .e.g. 64 kb/s, switching function whereby to carry narrow band services on a broadband network
As telecommunications networks increase in complexity and carry increasing volumes of traffic, the current procedures for setting up connections between subscribers are limiting the performance of these networks. In particular, congestion may be caused by attempting to connect to a subscriber who is already busy, or by attempting to choose a route through an already congested part of the network. Thus equipment and resources can be wasted in attempts to set up calls which cannot be completed. A further problem is that of scalability. As the network expands to accommodate increased traffic and a larger number of subscribers, there is an increasing need to facilitate integration of new equipment into an existing network without simply increasing the congestion problem.
The object of the invention is to minimise or to overcome these disadvantages.
According to one aspect of the present invention there is provided a distributed telecommunications exchange system having independent call routing and connection control for setting up connections across the system.
According to another aspect of the invention there is provided a telecommunications system, including an asynchronous transfer mode (ATM) network, and a plurality of adaptive grooming routers (AGR) coupled to the network, wherein the AGRs comprise a group adapted to function as a single distributed or virtual transit exchange whereby in use to set up narrow band connections across the ATM network.
According to one aspect of the present invention there is provided a distributed telecommunications exchange system having means for determining the current status of the system whereby to effect routing of narrow band traffic across the system.
According to another aspect of the invention there is provided a method of communicating resource availability to maintain performance of a distributed exchange system under overload conditions.
According to a further aspect of the invention there is provided a method of routing telecommunications traffic in a system including an asynchronous transfer mode (ATM) network having uncommitted bandwidth, and a plurality of adaptive grooming routers (AGR) coupled to the ATM network, which AGRs comprise a group adapted to function as a virtual transit exchange whose fabric and control are distributed over the group, the method including determining the current system status whereby to set up narrow band connections across the ATM network based on that status determination.
The technique provides for the separation of call routing and connection control together with the advertising of the system status. This ensures a wide range of scaleability so that the application of dynamic trunking technology provides scaleability in a traffic sense. Further, the separation of call routing and connection control provides a distributed computing environment which is scaleable and managed by this advertisement resource. Because the distributed exchange manages its own internal traffic, effectively it provides means for balancing that traffic to the fabric and makes its own internal routing decisions.
Reference is here directed to our co-pending United Kingdom patent applications Nos. 9410294.4, 9410295.1, 9411944.0 and 9502552.4 which relate to arrangements and methods for handling narrow band traffic in an ATM communications network.